<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        div{
            width:200px;
            height:100px;
            border:3px solid;
            transition: height 2s;
        }

        div.open{
            height:400px;
        }


    </style>
</head>
<body>
    <div class="open">
        aksdfjlask <br>
        aksdfjlask <br>
        aksdfjlask <br>
    </div>
</body>
</html>
<script>
    
</script>